late 15c., "absence of light;" 1610s with meaning "condition of being unknown;" from obscure (adj.) + -ity; or else from Middle French obscurité, variant of Old French oscureté "darkness, gloom; vagueness, confusion; insignificance" (14c.), from Latin obscuritatem (nominative obscuritas) "darkness, indistinctness, uncertainty," from obscurus.

When I was asked to talk about the Obscurity of the Modern Poet I was delighted, for I have suffered from this obscurity all my life. But then I realized that I was being asked to talk not about the fact that people don't read poetry, but about the fact that most of them wouldn't understand it if they did .... [Randall Jarrell, "The Obscurity of Poetry," 1953]